Detection of temporal delays in visual-haptic interfaces

This paper addresses the question of how large the temporal delay between a visual and a haptic stimulus may be such that the stimuli are still perceived as being synchronous. Participants had to judge whether the moment at which a graphical object collided with a virtual wall occurred simultaneously with the moment at which a force was felt through a force feedback joystick. Participants either moved the joystick to drive the object (active touch) or held the joystick in a steady position while the object moved by itself (passive touch). Participants were found to be very sensitive to visual-haptic time delays. Sensitivity was higher for passive touch than for active touch. The minimum delay at which participants judged the stimuli as asynchronous was on average 45 ms. The delay at which the proportion of synchronous judgments reached a maximum was on average close to zero. The results indicate that the temporal accuracy of visual-haptic interfaces has to meet stringent requirements in order to optimize the overall realism that users experience. Actual or potential applications of this research include teleoperation, medical training, computer-aided-design, and scientific visualization.